This invention relates to a running tool for use in a pipe, pipeline, wellbore or other tubular member (referred to hereinafter as a xe2x80x9ctubular member of the type specifiedxe2x80x9d), and which typically IS employed in the extraction of liquid or gaseous hydrocarbons, water, and also in geothermal applications.
In oil and gas wells, and in other boreholes, it becomes necessary from time to time to install, or change various devices in the well, and to perform investigative and other surveys. Most of these operations rely on the use of a xe2x80x9cwirelinexe2x80x9d, which may be one of two types, namely xe2x80x9cslicklinexe2x80x9d or xe2x80x9celectriclinexe2x80x9d. These terms are well known to those of ordinary skill in the art, and need not be described in detail herein.
A variety of tools and devices may be attached to a wireline, and lowered to the bottom of the wellbore, aided by gravity. Electricline has a conductor and insulator so that xe2x80x9cdownholexe2x80x9d tool responses can be electrically controlled, and measured from the surface as they happen. Slickline employs a single strand of wire, which can only be manipulated up or down to influence the tool or instrument operation in the wellbore.
Many wells are deviated in order that they may be drilled from a central point, but still be able to drain a large area. Deviated wells can have an angle of deviation of 70xc2x0 or more, but the greater the angle of deviation i.e. the greater the angle measured from the vertical and towards the horizontal, the greater will be the problem for wireline operations. Thus, the greater the deviation angle, the lesser will be the effect of gravity, and which can become overcome by the friction of the wire as it moves through the deviation angle, and the rolling resistance of the tools or other devices at the xe2x80x9cdownholexe2x80x9d end. The traditional remedy for this problem has been to increase the weight of the wireline, by adding heavy weight bars, and by reducing the rolling resistance of the tools and weight bars by adding wheels and centralisers.
Some wells have 90xc2x0, or near 90xc2x0 deviation, with correspondingly horizontal or near horizontal sections, and often running for thousands of feet, and this being situated at the bottom of a vertical shaft. These long horizontal sections or xe2x80x9clateralsxe2x80x9d are formed so as to improve drainage, or to access distant pockets of hydrocarbons.
In use of electricline systems, devices exist to pull the wireline along highly deviated, or horizontal sections, and such devices are known in the art as xe2x80x9ctractorsxe2x80x9d. These tractors convert a high voltage electrical supply which is passed down the insulated core of an electric wireline through a motor in the tractor which drives a hydraulic pump which is used to power a number of hydraulic motors. The motors are linked to wheels which are arranged around the body of the tractor, and positively drive it along the deviated section of the wellbore.
Electric line tractors can have a variety of tools and devices attached, for the purposes as described above. Such tools etc are selectively positioned in the wellbore, by powering the tractor until the required locations are reached. For subsequent retrieval of a tool, this is achieved by simply pulling on the cable after powering down the tractor.
The inherent nature of an electric wireline is such that an amount of special equipment for pressure control is required. Because the wireline is braided, the mechanism required for the prevention of well pressure escape is bulky and maintenance is intensive. The wire required to carry the high voltages associated with electric line tractors is not a type which would normally be available on site already, and the presence of high voltages in the presence and proximity of hydrocarbons raises severe safety questions during the operation of the equipment. Therefore, specialist personnel are normally required to operate the tractor equipment, in addition to the normal electricline crew. Electricline operations therefore, in general, are expensive.
Slickline wireline units, on the other hand, are almost universally present at production sites, and have simpler and more manageable pressure control equipment. The crew size is smaller, and slickline operations are therefore relatively inexpensive.
The invention therefore seeks to provide a running tool which is mechanically simple and does not require the complexity of operation, and cost of electricline operation, but which can be used with electricline, slickline, or any other wire or tubular system which is capable of reciprocating movement
According to one aspect of the invention there is provided a running tool which is intended to be lowered down a tubular member of the type specified, via a wireline extending from the surface to a connection to the upper end of the tool by which the tool is suspended, said tool being capable of advancing itself along the wall of the tubular member when required (e.g. when the tubular member is inclined to the vertical as a xe2x80x9clateralxe2x80x9d), by repeated application and release of tension force in the wireline, in which the tool comprises:
an assembly of a leading body portion and a trailing body portion, said portions being connected to each other so as to be linearly movable relative to each other in order to advance the tool along the tubular member;
a linearly displaceable actuator within the assembly and connectable to the wireline, said actuator being movable from a datum position in one direction relative to the assembly upon application of tension to the wireline;
means for converting relative movement of the actuator in said one direction to linear displacement of the leading body portion in an opposite direction;
respective wall-engaging means on each of the body portions which can be triggered alternately into gripping contact with the wall of the tubular member; and,
an energy source capable of being active between the body portions:
in which the tool has a cycle of self-advancing movement which comprises:
(a) application of tension via the wireline to the actuator so as to move the actuator in said one direction relative to the assembly;
(b) causing movement of one of said wall-engaging means into gripping contact with the wall of the tubular member to fix the respective body portion;
(c) storage of energy within said energy source as a consequence of the relative movement of the actuator;
(d) release of tension in the wireline thereby causing movement of the other of the wall-engaging means into gripping contact with the wall of the tubular member to fix the respective body portion and to cause release of said one wall engaging means;
(e) release of energy from said energy source so as to move the actuator relative to the assembly in an opposite direction to the datum position; aid,
(f) causing advancing movement of the leading body portion relative to the wall of the tubular member when its respective wall engaging means is released from gripping contact with the wall of the tubular member during the cycle of operation.
A reciprocating running tool according to one preferred embodiment of the invention therefore can move along a tubular member or wellbore, dragging a wire behind it, and carrying additional tools or instruments ahead of it. Motive force is provided by pulling on the wire from the surface, and the tool is run into the wellbore until such time that the frictional forces stop the tool from further descent. The tool has wall-engaging means in the form of dragblocks which allow movement in the downward direction only. Pulling on the wire at this time will anchor the lower part of the device to the wall of the tubular member (or wellbore), and will charge a spring and advances the main body (upper assembly) of the tool. On relaxing the wire, the upper assembly anchors itself to the wellbore, and the spring then discharges its spring force advancing the lower body downwardly, ready for the next cycle. As the wire is slackened off at this time, additional wire will be fed into the well, to compensate for the distance that the tool has moved. In this way, by repeatedly pulling and then slacking-off the wireline, the tool can be caused to advance along the wellbore by simple mechanical propulsion.
Tool retrieval may be affected by over-pulling on the wireline, in order to collapse the mechanism which locates the dragblocks (locking means). The mechanisms are normally located and biased by use of a spring of known force. When this force is overcome, the locating means is removed and the locking means may unlock. A similar mechanism is present in both the main body, and the upper portion of the tool. Once the locking means has become unlocked, it is retained in the unlocked position and the tool may be dragged out of the well.
However, it is within the scope of the invention to have an alternative sequence of operations, during a cycle of self-advancing movement, as provided by further preferred embodiments of the invention.
In these further preferred embodiments, the wall engaging means associated with the trailing body portion is movable into gripping contact with the wall of the tubular member upon relative movement of the actuator in said one direction so that said movement converting means is effective to move the leading body portion in an advancing direction simultaneously with storage of energy in the energy source, and in which the wall-engaging means associated with the leading body portion is moved into gripping contact with the wall of the tubular member and the wall-engaging means associated with the trailing body portion is released from gripping contact with the wall of the tubular member upon release of tension in the wireline, so that the energy stored in the energy source is effective to return the actuator to the datum position and to advance the trailing body portion towards the leading body portion.
According to a further aspect of the invention, there is provided a self-advancing tool for use in an underground passage and controllable from the surface by means connecting the tool to the surface, said tool being capable of advancing itself along the passage by repeated reciprocation of said means.